Re: [PATCH 1/4] perf tools: Allow to enable/disable events via control file

[Jiri Olsa <jolsa@redhat.com>]

On Tue, Jan 19, 2021 at 11:16:37AM -0300, Arnaldo Carvalho de Melo wrote:

SNIP

> >   terminal 2:
> >     bash 33349 [034] 149632.228023: sched:sched_process_fork: comm=bash pid=33349 child_comm=bash child_pid=34059
> >     bash 33349 [034] 149632.228050:   sched:sched_wakeup_new: bash:34059 [120] success=1 CPU:036
> >     bash 33349 [034] 149633.950005: sched:sched_process_fork: comm=bash pid=33349 child_comm=bash child_pid=34060
> >     bash 33349 [034] 149633.950030:   sched:sched_wakeup_new: bash:34060 [120] success=1 CPU:036
> 
> 'disable' doesn't seem to be working:
> 
> Terminal 3:
> 
> [root@five ~]# echo 'enable sched:sched_process_fork' > control
> [root@five ~]# echo 'disable sched:sched_process_fork' > control
> [root@five ~]# echo 'disable' > control
> [root@five ~]# echo 'disable sched:sched_process_fork' > control
> [root@five ~]# echo 'disable sched:sched_process_fork' > control
> [root@five ~]# echo 'enable sched:sched_process_fork' > control
> [root@five ~]# echo 'disable sched:sched_process_fork' > control
> [root@five ~]# echo 'enable sched:sched_process_fork' > control
> [root@five ~]# echo 'disable sched:sched_process_fork' > control
> [root@five ~]# echo 'enable' > control
> [root@five ~]# echo 'disable' > control
> [root@five ~]# echo 'disable' > control
> [root@five ~]# echo 'disable' > control
> [root@five ~]#
> 
> Terminal 1:
> 
> [root@five ~]# perf record --control=fifo:control,ack -D -1 --no-buffering -e 'sched:*' > perf.pipe
> Events disabled
> Event sched:sched_process_fork enabled
> Event sched:sched_process_fork disabled
> Event sched:sched_process_fork enabled
> Event sched:sched_process_fork disabled
> Events enabled
> 
> I tried also with '-o -', made no difference and:
> 
> [root@five ~]# perf record --control=fifo:control,ack -D -1 --no-buffering -e 'sched:*' -o - > perf.pipe
> Events disabled
> Event sched:sched_process_fork enabled
> Event sched:sched_process_fork disabled
> Event sched:sched_process_fork disabled
> 
> The second probably should be more clear stating that that event was
> already disabled.

ok, I'll make patch for that

> 
> Probably your example with all the sched tracepoints make 'perf record'
> just process the stream of events and not look at the commands?

hum, I'm not sure I understand what's the problem apart
from not printing that the event is already disabled
some events are not disabed?

> 
> If I try with:
> 
> [root@five ~]# perf list sched:sched_process_* 2> /dev/null
> 
> List of pre-defined events (to be used in -e):
> 
>   sched:sched_process_exec                           [Tracepoint event]
>   sched:sched_process_exit                           [Tracepoint event]
>   sched:sched_process_fork                           [Tracepoint event]
>   sched:sched_process_free                           [Tracepoint event]
>   sched:sched_process_wait                           [Tracepoint event]
> 
> [root@five ~]#
> 
> [root@five ~]# perf record --control=fifo:control,ack -D -1 --no-buffering -e 'sched:sched_process_*' -o - > perf.pipe
> Events disabled
> Events enabled
> Events disabled
> 
> It works.
> 
> So it is a pre-existing problem, I'll continue processing your patches
> and make a note about this...

ok, I'll check the note

thanks,
jirka